Recently, there have been a large number of developments of generators using nuclear power, waterpower, thermal power, tidal power, wind power, solar heat and the like, which are inexhaustible or clean energy sources, in view of exhaustion of underground resources and protection of the natural ecosystem all over the world. There are problems in that installation costs of conventional generators using underground resources as fuels are high, maintenance costs are continuously produced according to the use of the fuels, and wastes are produced due to the use of the nuclear or thermal power, thereby resulting in environmental pollution.
Therefore, there has been a need for use of a wind generator that can solve the problems of conventional propeller-type generators and is economical in view of its installation area and in which installation costs thereof is low and no pollutants are produced. A conventional wind generator generally comprises a body installed freely rotatably at an upper portion of a tower, propeller-type blades installed at a leading end of the body, a gearbox composed of a ring gear, planet gears and a sun gear for increasing rotational force of the blades, and a generator for generating electrical energy using rotational force from the gearbox.
The wind generator using the propeller constructed as such is disclosed in U.S. Pat. No. 4,291,233 and Korean Patent No. 57585.
First, the principle of the general wind generator will be discussed. A rotational speed of the blades of the wind generator is determined to obtain an ideal maximum linear velocity of the blades, which is 80 to 90 m/s, in the atmosphere having pressure of 1 atm. Then, the capacity and rotational speed of the generator are determined, and a gear ratio of the gearbox (ring gear, planet gears and sun gears) is determined. For example, when it is assumed that a rotational speed of a 600 kW generator is 1200 rpm, an outer diameter of the blades is 46 m and a rotational speed of the blades is 35 rpm, the gear ratio i of the gearbox becomes 34.3 (=1,200/35). Although a minimum wind velocity for starting the blades under such conditions is 3 m/s, the blades can be started when power required for rotation of the blades is larger than the load factor, which is resistance of the gearbox, in a state where the gears of the gearbox are engaged with one another.
However, in the conventional wind generators, huge costs and a substantial level of technical know-how are required for designing and manufacturing the wind generators to minimize power loss when the rotational force of the propeller-type blades rotated by wind energy is transmitted to the generator through the gearbox. The most important factor is the gearbox. Since a large resistance is exerted by the load of the weight of the blades and by the respective gears engaged with one another in the gearbox in a state where the rotational force (efficiency) of the gearbox is lowered or the rotation of the blades is stopped due to very gentle winds, the blades cannot be started even though a gentle wind having a minimum wind velocity required for the starting of the blades blows. Thus, the expensive wind generator becomes useless.
Furthermore, since the conventional wind generators are constructed such that the body having the blades rotates about the tower so as to allow the positions of the blades to freely change depending on wind direction, the blades are prevented from stopping due to a change in wind direction so that the force for generating electricity can be obtained. However, there is a problem in that if the wind direction suddenly changes such as by a gust, the rotation of the blades may stop and the blades may also be severely jolted and then broken.